Cold Weather Conundrum

alexd

I run a Hoffman 2-pipe with differential loop system and in the 10 years I’ve lived in my house have made a number of incremental improvements over the years to get it working reasonably well (thanks in large part to this forum, and in particular to @Jamie Hall). Then came this recent cold snap - the system is running nonstop and can’t heat the house above 58 degrees. It’s a big stone house that loses a lot heat, but many of the radiators are not even heating despite the boiler running continuously.

This has been a very cold week (for Philadelphia where I am) with overnight temps in the single digits and day time highs in the teens. That said, we’ve had cold snaps like this before and the system has never struggled so much to keep up.

Under normal circumstances the heat isn’t perfectly even, but there are now several radiators that normally work well that are getting no heat at all, which I’m sure is contributing to the low indoor temp and the constant call for heat.

A few things to note in trying to solve this mystery:

• vaporstat set at 8oz in/4oz out
• Gorton #2 main vent on top of differential loop
• Crown Boiler 262,500 input BTU. Manufacture date is 2001.
• Crossover traps working per IR gun
• Steam mains are mostly insulated, and hot all the way to end
• Near boiler piping is undersized, but has always been this way
• Some radiators are outside the original envelope in a sunroom that gets very cold; they seem to be working fine though
• No evidence of steam in dry return, or traps that are passing steam
• Some radiators will go completely cold, then heat up 2 hours later

I can’t figure out what’s keeping steam from entering radiators, or where it’s all going. The system isn’t building pressure or tripping the differential (runs continuously), and it’s not calling for water. I’ve replaced cage units in some traps and verified they’re working correctly, but even these rads are not heating. Seems like it must be some sort of pressure issue that’s preventing air or water from exiting the radiators, but not sure what’s causing this or how to resolve.

Appreciate any input or advice on things to investigate or try. I’m curious to see if this resolves when the weather warms, or if it’s a different problem that will persist (do I just need a new boiler??). And FWIW I have tried for years to find a knowledgeable steam professional willing to work in my area with no luck, so if anyone has recommendations there I also appreciate it As others in my area have noted in the forum, the companies listed under “find a pro” say they don’t work in Philadelphia, and other people I’ve called suggest putting vents on my radiators - no thanks.

delcrossv

Try removing the Gorton #2 and run a cycle with open pipe. Any way the returns are possibly sagged and full of water?

bburd

The symptoms you describe, with the burner never shutting off on pressure and the system not filling with steam or losing water, are consistent with underfiring. It's possible that your burner is not firing at its normal rate.

If it's a natural gas burner and the region is having a severe cold snap, pressure in the gas mains may be lower than normal, or you might have a frozen regulator.

You can clock the gas meter to see how much it's actually firing. Does the flame look normal?

EBEBRATT-Ed

I agree with @bburd.

Sounds like your underfired.

ratio

It also could be just plain too small to heat properly in this kind of weather. Some radiators are stealing all the steam so it can't make it to the others.

Maybe close off one or two of the hottest & see if the steam goes somewhere else.

alexd

I clocked the meter based on instructions I found here and it would appear the boiler is under firing, by a lot.

Rating plate is 262,500 BTU, and I’m getting 124,500. (Formula is 30 seconds for one cubic foot, so 3600/30 x 1035BTU).

Not sure what the flame should look like, but can see a fair amount of orange, and flickering, which seems not good?

is there a way to determine whether the problem is related to gas pressure vs. the boiler?

BobC

I had this happen to me several years ago. The gas pipe coning in from the street had a lot of rust partially blocking the flow of gas. The gas company replaced the pipe and that solbed the problem.

Bob

Steamhead

https://forum.heatinghelp.com/discussion/comment/1837539#Comment_1837539

This has happened to a few of our customers this season. Have a pro come in and measure the incoming gas pressure, then contact the gas company if it turns out to be low.

alexd

Update: gas company came out to check the pressure. They checked water column and confirmed pressure is good. They also confirmed my clocking measurement which shows the boiler is severely under fired. They advised to get the gas control valve repaired or replaced asap, which is my next step.

Since it’s been running this way for a while I don’t see a reason not to keep running it to avoid pipes freezing for the next few days until I can get a plumber out, but if anyone thinks there’s a safety risk or further damage may occur I could try alternatives.

It’s possible that the valve has been downfired like this for a long time, but seems like something else is going on since the system is still struggling to get the house to 60 (outdoor high of 27 today).

jesmed1

@alexd Hopefully a replacement valve is still available. You might find this helpful, as the owner had a Crown boiler of similar vintage:

https://forum.heatinghelp.com/discussion/194706/obsolete-gas-valve